In a conventional tyre of the tubeless type, the radially internal face comprises an airtight layer (or more generally a layer airtight to any inflation gas) which makes it possible to inflate the tyre and to keep it under pressure. Its airtightness properties allow it to guarantee a relatively low level of pressure loss, making it possible to keep the tyre inflated in a normal operating state for a sufficient period of time, normally of several weeks or several months. Another role of this layer is to protect the carcass reinforcement and more generally the remainder of the tyre from the risk of oxidation due to the diffusion of air originating from the space interior to the tyre.
This role of airtight inner liner or interior rubber is today fulfilled by compositions based on butyl rubber (copolymer of isobutylene and isoprene), which have been recognized for a very long time for their excellent airtightness properties.
However, a well-known disadvantage of the compositions based on butyl rubber or elastomer is that they exhibit high hysteresis losses, furthermore over a broad temperature spectrum, which disadvantage is damaging to the rolling resistance of the tyres.
To reduce the hysteresis of these airtight inner liners and thus, in the end, the fuel consumption of motor vehicles is a general objective which current technology comes up against.
The document WO 2008/145277 of the Applicant companies discloses an inflatable article provided with a layer airtight to the inflation gases, in which the inner liner comprises an elastomer composition comprising at least one copolymeric thermoplastic elastomer comprising polystyrene and polyisobutylene blocks and a polybutene oil.
In comparison with a butyl rubber, the TPS elastomer exhibits the major advantage, due to its thermoplastic nature, of being able to be worked as is in the molten (liquid) state and consequently of offering the possibility of simplified processing.
However, under some rolling stresses, the temperature stability of such an airtight layer based on TPS elastomer may prove to be inadequate, in particular at high temperature and under stress.